This invention relates generally to the fuel delivery systems of engines and more particularly to a method and apparatus for delivering fuel in a manner to achieve more complete combustion.
It has long been known that liquid fuel precipitates out of the air-fuel mixture in the intake manifold of a conventional internal combustion engine. The fuel liquification often occurs under the carburetor on the plenum floor near the junctions of the manifold conduits with the plenum, and this is caused primarily by the change of direction that occurs at these locations. Liquification also occurs at the dividers between the manifold conduits and at any places where there are turns or other disruptions of the flow.
The liquid fuel is eventually sucked into the cylinders where it is burned along with the fuel that remains in suspension. However, the atomized fuel that is suspended in the air-fuel mixture burns much more quickly and completely than the liquified fuel because its atomized state increases its dispersion and the area to volume ratio of the fuel droplets. The liquified fuel burns incompletely and creates numerous problems, including increased exhaust emissions, decreased engine power, reduced fuel economy, noisy operation, engine knock, fouling of the cylinders, cold starting problems and overall performance fall off.
The existence of the fuel precipitation phenomenon and the problems it causes have long been recognized. For example, U.S. Pat. No. 1,810,917 to Kreis teaches an arrangement in which the liquified fuel is collected in a trap in the intake manifold and is directed in liquid form through a passage leading to the engine cylinder. Although this removes the liquified fuel from the fuel intake system, it does little if anything to improve the combustion efficiency. The fuel is supplied in liquid form to the cylinders rather than as finely atomized droplets dispersed in the air, and the liquified fuel is burned incompletely to cause many if not all the problems previously noted. U.S. Pat. No. 2,201,014 to Scheerer discloses a similar arrangement except that the fuel from the traps is circulated back to the suction side of a charging blower rather than directed to the cylinders.
Particularly in recent years, fuel injectors have achieved considerable popularity. Although the use of fuel injectors generally eliminates the fuel precipitation problem that is associate with carburetor systems, the fuel injectors have problems of their own. Perhaps most notably, the injector must have an extremely small injector port in order to assure that the injected fuel is finely atomized so that efficient combustion takes place. However, the hair sized ports that are required are so small that they are highly susceptible to clogging by small particles of dirt or other foreign materials that are inevitably present in the fuel from time to time. Consequently, the injector ports frequently become clogged and must be cleaned or replaced before the engine can operate efficiently.